The Impact of Omega-3 Fatty Acids on Heart Health

Updated July 2026

Omega-3 fatty acids are one of the four building blocks of heart health we formulate around at Step One, alongside whole food fiber, antioxidants, and plant sterols. They are also behind one of the most common questions I get in my clinic: should I be taking a fish oil supplement? The honest answer has shifted over the past decade, and it helps to understand why.

What are omega-3 fatty acids?

Omega-3s are a family of healthy fats that come in three forms. ALA, or alpha-linolenic acid, comes from plants. EPA and DHA come mainly from fish and seafood. ALA is the one your body cannot make on its own, which makes it an essential fat you have to get from food. Your body can convert a small amount of ALA into EPA and DHA, but the conversion is limited, which is why fish is the most direct source of the marine forms. For the bigger picture on how all the dietary fats compare, I laid it out in which fats are good and bad for your heart.

Do omega-3s actually protect the heart?

The strongest evidence points to omega-3s from food, not from pills. People who regularly eat fish and plant sources of omega-3s tend to have lower rates of heart disease, a pattern that has held up across large populations for decades. For plant-based ALA in particular, higher intakes have been linked to a lower risk of fatal heart events. Interestingly, ALA has little effect on LDL cholesterol, so some of its benefit may come from lowering inflammation rather than from changing your cholesterol numbers.

Should I take a fish oil supplement?

For most people, no, and this is the part that has changed. When researchers put fish oil supplements to the test in large randomized trials, the results were mostly disappointing. VITAL and ASCEND, two of the biggest, found that a daily one-gram fish oil capsule did not meaningfully reduce major cardiovascular events like heart attack, stroke, and cardiovascular death, whether in the general population or in people with diabetes. The STRENGTH trial, which tested a higher-dose combination of EPA and DHA, was stopped early when it became clear it was not helping. Taken together, the evidence does not support fish oil supplements for preventing heart disease in the average person.

There is one exception worth knowing, because patients ask about it. A prescription form of purified EPA, called icosapent ethyl (Vascepa), reduced cardiovascular events by about 25% in the REDUCE-IT trial. But that benefit showed up in a specific group: people already on a statin who still had high triglycerides and high cardiovascular risk. It is a prescription medication for a narrow, well-defined situation, not a reason to buy fish oil off the shelf. As an interesting aside, the trial itself has since been criticized as the "placebo" tablet was mineral oil — which could have had a negative effect, enhancing Vascepa's apparent positive one.

Can fish oil supplements be harmful?

They are not risk-free, especially at higher doses. Several large analyses have found that omega-3 supplements raise the risk of atrial fibrillation, an irregular heart rhythm that increases the chance of stroke. The risk tracks with the dose. It is modest below one gram a day and climbs noticeably above it. So reaching for a big fish oil capsule "just in case" can carry a real downside for very little proven upside.

What is the best way to get your omega-3s?

Eat them, don't swallow them in a pill. The American Heart Association recommends eating fish, especially fatty fish like salmon, at least twice a week. For plant-based omega-3s, ground flaxseed, chia, walnuts, and canola and soy are all rich in ALA. A single tablespoon of ground flax delivers about 1.6 grams, and an ounce of walnuts about 2.6 grams. When omega-3s arrive inside real food, you also get the fiber, protein, and other nutrients packaged alongside them, and none of the arrhythmia risk that comes with concentrated pills.

This is exactly why we build omega-3s into Step One Foods through whole-food ingredients like flax and walnuts rather than added oils. Two servings a day supply 2 grams of plant-based ALA, delivered the way nature intended, as part of the food rather than extracted into a capsule.

If you're new to this site and found this useful, I write one of these evidence-based articles every week. You can get them in your inbox by joining my email list at the bottom of this page. No spam, no requirement to buy anything, just practical knowledge.